The present application is a continuation-in-part of application Ser. No. 029,733 filed on Mar. 24, 1987 now abandon.
This invention generally pertains to a pneumatic door operator construction. More specifically, the present invention relates to a sliding door operator system which utilizes a rodless fluid cylinder for mechanically opening and closing a door.
The invention is particularly applicable to sectional overhead doors of the multiple panel type in which the door is aided in being raised and lowered by a counterbalance means such as a torsion bar and will be described with particular reference thereto. However, it will be appreciated by those skilled in the art that the invention has broader applications and may also be adapted for use in many other environments such as single panel overhead lift doors, overhead roller doors, bi-parting doors, and even sideward sliding doors or the like.
Most overhead doors are counterbalanced with a torsion spring or a counterweight system for storing energy during door closing so that energy may be extracted during door opening. During opening, most of the energy for lifting such a door is derived from the energy stored in the spring or counterweight system. If the door is counterbalanced fairly well, the amount of manual energy required to open the door need only be sufficient to make up the frictional and other losses in the system. During door closing, the energy required is that for making up the frictional and other losses since most of the energy which is transferred to the spring or counterweight storage system is derived from the weight of the descending door.
In general, conventional overhead doors of this nature are suspended by a cable which is wound around a drum axially driven through a shaft by the torsion spring with the shaft being rotated by a chain driven sprocket. Generally, the chain is driven by an electric motor. In some environments, however, the use of electrical motors is undesirable because of the possible danger of a spark causing an explosion or a fire. It has also been found that electric motors are disadvantageous since if the door becomes jammed the motor will continue rotating and will likely unwind the cable between the drum and the door and this could prove hazardous to personnel and may damage property.
Also, when such doors go through a high number of cycles, such as in a car or truck wash, or in factories, warehouses or the like, the electrical motors, and bearings wear out at a fairly rapid rate and this results in frequent breakdowns of the door opening mechanism. Moreover, malfunctions of the door opening mechanism sometimes also lead to damage to the torsion spring mechanism of the door which can be fairly expensive to repair.
Some conventional trolley type and jack shaft type pneumatic cylinder door operators are known to the art. However, every one of these includes a piston rod extending out of the cylinder which increases the length of the operator and the amount of room necessary to mount the operator.
One recent suggestion has been to utilize a pair of pneumatic cylinders in a side mounted operator for moving the chain of the chain driven sprocket by the use of piston rods thereby rotating the sprocket. However, side mounted operators are not recommended when a trolley operator could be used in their place since with a side mounted operator any hesitation in door travel results in an unwinding of the cable from the torsion bar drum which makes the door liable to a free fall that could cause grave injury to people as well as damage to objects under the door and to the door itself.
For certain types of doors, such as high-lift type vertical lift doors and roll up type doors, a trolley operator cannot be used and thus a side mounted so-called jack shaft operator has to be used. The conventional electric motor powered jack shaft operators are disadvantageous for the reasons previously mentioned. The side mounted dual piston type system is also disadvantageous since the design of this system will produce a constant downward torque on the main door shaft and also will exert an unnecessarily heavy load on the end bearing where the shaft is suspended. This wears the bearing and can cause the bearing plate to cut through the shaft. With this type of operator, the chain can jump the sprocket and the cable can jump the drum every time the door hesitates during its travel, or the chain goes slack, or if the shaft becomes bent at some point during door operation. Another difficulty with the conventional side mounted pneumatic cylinder system is that it is mounted near the bottom of the door and in this location the door track may get hit by a vehicle which can also damage the cylinders. In addition, in wet and cold environments, moisture in the air can freeze in the cylinders thereby damaging the seals on the piston rod and causing air leaks and hence a malfunction of the door. In addition, on relatively low doors, i.e. 7 to 10 foot high doors, the chain of the conventional dual piston system can be hazardous to personnel since the chain is so located that it can entangle the limbs, or hair, of personnel.
Accordingly, it has been considered desirable to develop a new and improved jack shaft type door operator system which could be mounted either horizontally normal to the closed door or vertically parallel to the door and would overcome the foregoing difficulties and others while providing better and more advantageous overall results.